Topic 4.4

• CO2 (cell resp. burning fossil fuels) • Water vapour (evaporation, transpiration)

• Methane (marshes, organic landfill sites, extraction of fossil fuels) • Nitrogen oxides (naturally by bacteria, agriculture, vehicle exhausts)

Water droplets on clouds retain heat during day and at night re-radiate heat back to the surface

Water droplets in clouds reflect a range of different wavelengths in both directions (including radiation coming inward that would have been re-emitted as heat)

• Ice cores drilled in Antarctic ice sheets • Core shows annual layers, used to date air bubbles trapped in the ice • Analysis of the gas content of the bubbles gives both concentration of CO2 in the atmosphere and the air temperature (from O2 isotopes) during the time the ice was formed

• higher global average temperatures • more frequent and intense heat waves • some areas becoming more prone to droughts • more evaporation of water from oceans • some areas more prone to intense periods of rainfall and flooding • tropical storms more frequent and powerful • changes to ocean currents

• ocean absorbs around 25% of CO2 emitted to the atmosphere • more CO2 in ocean results in acidification, since 1800, pH of seawater has fallen by 0.1 pH units or 30% increase in acidity

• dissolved free CO2 • carbonic acid (H2CO3) • bicarbonate (HCO(-3)) • carbonate (CO3 (2-)) Formation of carbonic acid, bicarbonate and carbonate release H+ ions, further decreasing the pH of seawater

Marine calcifying species - oysters, clams, sea urchins, shallow water corals, deep sea corals, calvados’s plankton Need to absorb carbonate ions from seawater to make CaCO3 in their skeletons

Photosynthetic algae and sea grasses Low CO2 is a limiting factor for photosynthesis